1. Field of the Invention
The present invention relates to a method of detecting and analyzing a defective portion of a semiconductor element, and more particularly, a method of detecting and analyzing a defective portion by means of an emission microscope. The present invention also relates to an apparatus for detecting and analyzing the same.
2. Description of the Related Arts
The manufacture of a semiconductor device are performed such that semiconductor elements such as a transistor, a resistor, a diode, etc., are formed as quite fine patterns at a small area of a semiconductor substrate, and that the formed semiconductor elements are electrically connected by wiring techniques so as to accomplish a desirable circuit function of the semiconductor device.
In this kind of semiconductor device, attempts are made to make the patterns finer and also make the electric consumption current lower, in the development in the semiconductor technology, so as to improve the integration. However, this improvement of the integration has the drawback of difficulty in detecting a defect within the semiconductor device. Namely, since a leak current due to a defect to be detected, becomes quite weak in proportion to such pattern reduction and consumption current lowering, the accuracy of the detection is apt to be degraded by the noise etc., of the detection device.
In order to overcome such a drawback and detect such a small leak current by higher sensitivity, there is a method of detecting such a defective portion by use of an emission microscope, which detects a small amount of light emitted from the defective portion.
This detecting and analyzing method by use of the emission microscope is conducted as following. Namely, at first the semiconductor device to be examined is set on a stage of the emission microscope to which an image processing apparatus is connected, in such a condition that the semiconductor device can be supplied with an external electric current. An objective lens having the minimum magnification, is set. The pattern image of the semiconductor element is stored into a first memory included in the image processing apparatus.
Then, the electric voltage is applied to the semiconductor element so that the symptom of the defect appears. The small amount of light emitted from the defective portion of the semiconductor element, is detected by the emission microscope, and the emitted light is integrated for a predetermined time period, and the integration result is stored into the second memory.
Then, the data in the first memory and the data in the second memory are read out therefrom, overlapped with each other by the image processing apparatus and displayed on a monitor. At this time, if necessary, the displayed image is outputted to a hardcopy apparatus and recorded by the hardcopy apparatus.
Then, the light emission portion detected in the above detecting operation, is placed to the center of the stage of the emission microscope. The objective lens having a higher magnification, is set in the emission microscope.
The above described processes from the data storing process into the first memory, to the objective lens setting process, are repeated until a desirable magnification for the pertinent light emission portion is obtained.
If there are a plurality of light emission portions, the whole process from setting the minimum magnification objective lens, is repeated until the detection processes are completed for all of the light emission portions.
In this manner, the defective portions can be detected and analyzed by use of the leak current caused in the semiconductor element, according to this detecting technique by means of the emission microscope.
In the above described defective portion detecting and analyzing method, however, the process of placing the light emission portion to the center of the stage of the emission microscope, is manually performed by the operator for each necessary occasion, which results in increases of the operation time and the labor of the operator. Particularly, since the light emission portion to be examined can be easily lost during the operation of changing the magnification, the increases of these time and labor of the operator are serious.
Further, according to the above described detecting method, in case that a plurality of light emission portions exist on one semiconductor substrate, since it is necessary to reset the magnification to its minimum value for each light emission portion in order to check its position, the time required to determine the defective portion becomes quite long.
Furthermore, according to the above described detecting and analyzing method of the related art, the recognition of the light emission portion depends on the observer as he distinguishes a plurality of light emission portions from the noises in the observed image, which is basically formed by integrating the emitted lights during a certain time period. Accordingly, the detection result of the defective portion depends on the skill of the observer, and there is a high possibility that the observed light emission portion, is incorrect, due to the mistake of the observer based on the noises of the emission microscope. In this manner, the difference in the observation result due to the individual variations, is a problem in this kind of detecting and analyzing method. This further leads to such a problem that the working load on the observer accompanied with the aforementioned troublesome movement of the stage of the emission microscope as well as the time required to perform the detection, is increased, while this time consuming and troublesome detecting operation itself causes the secondary defect in the tested object i.e. the semiconductor substrate, which is an essentially delicate article. On the other hand, the fact that the observed image is actually formed by integrating the emitted lights during the certain time period in the emission microscope, makes it difficult to perform an automatic detecting and analyzing procedure.